i have heard about people using shell rotella or other diesel engine oils in their motorcycles, usually because of an "assumed" cost savings.
the rotella i know is conventional oil, not semi or full synthetic, and has more detergents than you'll ever need or want, in a new gasoline engine.
why not use the correct oil, and a quality filter (you know that wix is a very budget minded filter) ? personally, i think you'd be money and some engine parts wear ahead) using the proper m/c oil, in the proper viscosity, with a quality filter. . . and just extending your oil change schedule to the manufacturers specs. just my .02 cents. :wink: